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Object Oriented Programming

Object oriented programming in Python is accomplished through the use of classes, inheritance, and encapsulating data.

Classes​

Classes can be created with the class keyword.

class Employee:
    def __init__(self, name, age):
        self.name =  name
        self.age = age

alice = Employee("Alice", 30)
bob = Employee("Bob", 32)

__init__ is used as a constructor.

Instance methods​

Instance methods in python are basically public functions which can be called on the instance of the class to manipulate the class state.

class Employee:
    def __init__(self, name, age):
        self.name =  name
        self.age = age

    # Instance method
    def description(self):
        return f"{self.name} is {self.age} years old"

Self is similar to this is JavaScript. It is a reference to the instance of the class.

Static methods​

Static methods are functions that are bound to the class definition and not an instance of the class. They can be created in two ways.

  1. Defining the method within a class and then using the staticmethod function to make it a static method.
class Calculator:

    def addNumbers(x, y):
        return x + y

# create addNumbers static method
Calculator.addNumbers = staticmethod(Calculator.addNumbers)

print('Product:', Calculator.addNumbers(15, 110))
  1. Using the attribute @staticmethod during the initial function definition. This way is cleaner and easy to maintain.
class Calculator:

    # create addNumbers static method
    @staticmethod
    def addNumbers(x, y):
        return x + y

print('Product:', Calculator.addNumbers(15, 110))

Inheritance​

Inheritance allows once class to take variable and function definitions from another class. The new class is the child class that inherits from the parent class.

class Parent:
    hair_color = "brown"

class Child(Parent):
    hair_color = "purple"

In this example, the Child instance inherits from Parent, but overrides the shared variable called hair_color and sets it to purple.